Updated timing for thunderstorm Monday night and closer look at the threats

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Eyes are watching an area over eastern Iowa and northwest Illinois for thunderstorm development this evening. It will be these storms that will impact central Indiana late Monday night through early Tuesday morning.

Computer model projection of radar/satellite imagery.

Computer models suggest this could start to happen as early as 7:00 p.m. to 8 p.m. Monday.

The storms are expected to move east across north-central Illinois Monday night. The thunderstorms will merge into a larger complex of thunderstorms, referred to as a mesoscale convective system (MCS), and eventually shift to a southeastward trajectory.

Latest data suggests we could see the complex of thunderstorms arriving in central Indiana between midnight and 1 a.m. Tuesday.

Computer model projection of radar/satellite imagery.

The complex is expected to keep moving southeast towards the Indianapolis metropolitan area, arriving between 2 a.m. and 3 a.m.

Computer model projection of radar/satellite imagery.

The MCS should be moving out of the CBS4 viewing area between 5 a.m. and 6 a.m.

Computer model projection of radar/satellite imagery.

Due to the timing of the storms, most will be asleep. That is why it is important that you turn on your NOAA weather radio prior to going to bed tonight. You can also download The Weather Authority app to your iOS and Android devices. The app is free and will send out notifications when warnings are issued. (Tip: Make sure notifications are enabled for overnight hours.)


Several modes of severe weather will be possible tonight. Damaging winds is the main threat when we look at the overall storm assessment.

Probability of winds or wind gusts of 57 mph or higher according to the Storm Prediction Center.

The Storm Prediction Center indicates a 30% probability of winds or wind gusts of 57 mph or greater through 8 a.m. Tuesday morning for areas shaded in orange and a 15% or greater probability for areas shaded in yellow.

Due to the strong winds, there will be a chance for limbs and trees to be knocked down, which could lead to power outages along the path of the complex of thunderstorms.

Our high-resolution computer model projects areas of isolated and scattered power outages. The outages could be more widespread in some areas that may be heightened to widespread outages. Again, it will depend on the track of the complex of thunderstorms, so the path could be 30-40 miles north or south of what the image above shows. Nonetheless, know that power outages are a possibility while you’re sleeping. In other words, make sure you have a battery powered alarm clock option if you need to be up by a certain time Tuesday morning.

While the risk of a tornado remains low, there still is a possibility of an isolated tornado overnight. The latest computer modeling data from the Storm Prediction Center highlights areas from eastern Iowa to northwest Ohio for having the best ingredients in the atmosphere for producing a tornado.

Overall, the highest risk for a tornado exists in eastern Iowa and north-central Illinois with discreet thunderstorms.

Some areas can also expect to get brief, heavy rain from the overnight thunderstorms.

Computer model projection of rainfall accumulation through Tuesday morning.

You may have noticed the high humidity today. That is a lot of moisture for thunderstorms to work with and put down to the ground in the form of rain. Don’t pay attention to the exact location/rainfall amounts, know that where the MCS passes over, the potential is there for 1″ to 2″ of rain in a short period of time.

Flash Flood Guidance suggests 1.5″ to 2″ of rain falling in a 3 to 6 hour time frame could produce flash flooding. So the potential for street flooding does exist overnight, and it isn’t out of the question that there could be high water on some roads for the Tuesday morning commute.

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